Method and device for constraining codebook subset

ABSTRACT

The embodiments of the present disclosure provide a method and a device for constraining a codebook subset. The method includes steps of: determining codebook subset constraint parameters for all or parts of matrix sets for constructing a codebook respectively, each codebook subset constraint parameter indicating an available matrix in a corresponding matrix set; and transmitting the determined codebook subset constraint parameters to a UE. The number of the matrices in each matrix set for constructing the codebook is far less than the number of precoding matrices in the codebook.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of PCT Application No.PCT/CN2016/078023 filed on Mar. 31, 2016, which claims priority toChinese Patent Application No. 201510250857.3 filed on May 15, 2015, thedisclosures of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present disclosure relates to the field of wireless communicationtechnology, in particular to a method and a device for constraining acodebook subset.

BACKGROUND

A closed-loop precoding technology has been introduced into a Long TermEvolution (LTE) Release 8 (Rel-8) system so as to improve the spectralefficiency. For the closed-loop precoding technology, at first anidentical set of precoding matrices, i.e., a codebook, is required to bestored at a base station and a User Equipment (UE). Upon the estimationof channel information in accordance with a cell common pilot signal,the UE selects one precoding matrix from the codebook in accordance witha certain criterion, e.g., maximum mutual information or maximum outputSignal-to-Interference and Noise Ratio (SINR). Next, the UE feeds anindex of the selected precoding matrix, i.e., a Precoding MatrixIndicator (PMI), in the codebook back to the base station through anuplink channel. Finally, the base station may determine the precodingmatrix to be used by the UE in accordance with the received index. Theprecoding matrix reported by the UE may be considered as a quantizedvalue of Channel State Information (CSI).

In a conventional cellular system, antennae of the base station areusually arranged horizontally in an array form. Beams from a transmitterof the base station are merely adjusted in a horizontal direction, andeach beam is provided with a fixed down-tilt angle in a verticaldirection for each UE. Hence, various beamforming/precoding technologiesare adopted on the basis of channel information in the horizontaldirection. However, actually a radio signal is transmitted in the spacein a three-dimensional (3D) manner, so it is impossible to provideoptimal system performance through the fixed down-tilt angle. The beamadjustment in the vertical direction plays a very important role in theenhancement of the system performance. Along with the development of theantenna technology, an active antenna capable of controlling eachelement independently has currently emerged. Through this kind oftwo-dimensional (2D) antenna array, it is possible to dynamically adjustthe beams in the vertical direction. For a Frequency Division Duplexing(FDD) system, a three-dimensional beamforming/pre-coding operation needsto be performed on the basis of the CSI reported by the UE. As apossible way, the CSI may be reported on the basis of the codebook, likethat adopted by the LTE Rel-8 system all the time.

The codebook for the feedback of the CSI needs to conform with both aconfiguration of the antenna array and an application scenario, so as toreturn the CSI accurately. In the case that the 2D antenna array isadopted, there may be a large number of possible application scenarios.In order to match all the possible configurations of the antenna arrayand application scenarios, a size of the designed codebook will be verylarge, resulting in large uplink feedback overhead and largeimplementation complexity at a UE side. One scheme is to constrain acodebook subset, so as to limit available precoding matrices in thecodebook, thereby to reduce the implementation complexity at the UEside. In a conventional method for constraining the codebook subset,with respect to each precoding matrix in the codebook, the base stationmay use a one-bitmap to indicate whether or not the precoding matrix isavailable for the UE. For example, in the case that an indicator bit hasa value of 1, it means the precoding matrix is available, whereas in thecase that the indicator bit has a value of 0, it means the precodingmatrix is unavailable. However, the codebook for the 2D antenna arraymay contain a huge number of precoding matrices, e.g., 4096 or even moreprecoding matrices. At this time, a large number of system resources maybe occupied in the case that each precoding matrix is indicated usingthe bitmap.

SUMMARY

An object of the present disclosure is to provide a method and a devicefor constraining a codebook subset, so as to solve the problem in therelated art where a large number of system resources are occupied.

In one aspect, the present disclosure provides in some embodiments amethod for constraining a codebook subset, including steps of:determining codebook subset constraint parameters for all or parts ofmatrix sets for constructing a codebook respectively, each codebooksubset constraint parameter indicating an available matrix in acorresponding matrix set; and transmitting the determined codebooksubset constraint parameters to a UE.

In a possible embodiment of the present disclosure, the step ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively includes:determining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with a configuration of an antenna array; or determining thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with anapplication scenario; or determining the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook respectively in accordance with the configuration of theantenna array and the application scenario; or determining the codebooksubset constraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with a measurementresult of an uplink signal transmitted by the UE; or determining thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance withinformation returned by the UE; or determining the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance withmatrix-available information reported by the UE.

In a possible embodiment of the present disclosure, the step ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the measurement result of the uplink signal transmittedby the UE includes: measuring the uplink signal transmitted by the UE soas to obtain the measurement result; determining whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with the measurement result; and determining the codebooksubset constraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, the step ofmeasuring the uplink signal transmitted by the UE so as to obtain themeasurement result includes measuring the uplink signal transmitted bythe UE, so as to obtain a horizontal azimuth angle or a vertical azimuthangle of the UE. The step of determining whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith the measurement result includes calculating an array responsevector correlation coefficient between each matrix in each matrix subsetfor constructing the codebook and the horizontal azimuth angle or thevertical azimuth angle, comparing the array response vector correlationcoefficient with an array response vector correlation coefficientthreshold, and determining whether or not the matrix is available inaccordance with a comparison result.

In a possible embodiment of the present disclosure, the step ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information returned by the UE includes: rankingprecoding matrices in a descending order of usage times, selecting apredetermined number of precoding matrices with the largest usage timesin accordance with the information returned by the UE within apredetermined time period, and determining matrices corresponding to theselected precoding matrices; calculating a correlation coefficientbetween each matrix in each matrix set for constructing the codebook andeach of the determined matrices corresponding to the selected precodingmatrices, comparing the correlation efficient with a matrix correlationcoefficient threshold, and determining whether or not the matrix in eachmatrix subset is available in accordance with a comparison result; anddetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with a determination result.

In a possible embodiment of the present disclosure, the step ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information about the matrix-available informationreported by the UE includes: determining whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith an available matrix indicated in the matrix-available informationreported by the UE, and determining the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook in accordance with a determination result; or determiningwhether or not each matrix in each matrix set for constructing thecodebook is available in accordance with an unavailable matrix indicatedin the matrix-available information reported by the UE, and determiningthe codebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook in accordance with a determinationresult; or determining whether or not each matrix in each matrix set forconstructing the codebook in accordance with a matrix-available weightvalue indicated in the matrix-available information reported by the UE,and determining the codebook subset constraint parameters for all orparts of the matrix sets for constructing the codebook in accordancewith a determination result.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter is a bitmap, and each bit in the bitmap correspondsto a matrix in the matrix set and is used to indicate whether or not thematrix is available; or each codebook subset constraint parameterincludes a set of index values, and each index value corresponds to anavailable matrix in the matrix set; or each codebook subset constraintparameter is a bitmap, and each bit in the bitmap corresponds to amatrix subset in the matrix set and is used to indicate whether or notthe matrix subset is available; or each codebook subset constraintparameter includes a set of index values, and each index valuecorresponds to an available matrix subset in the matrix set.

In a possible embodiment of the present disclosure, the method furtherincludes: determining an active codebook of the codebook; generating abitmap corresponding to the active codebook, each bit in the bitmapcorresponding to a precoding matrix in the active codebook and beingused to indicate whether or not the precoding matrix is available forcalculating and returning CSI; and transmitting the bitmap correspondingto the active codebook to the UE.

In another aspect, the present disclosure provides in some embodiments amethod for constraining a codebook subset, including steps of: receivingcodebook subset constraint parameters corresponding to all or parts ofmatrix sets for constructing a codebook, each codebook subset constraintparameter indicating an available matrix in a corresponding matrix set;determining available matrices in each matrix set for constructing thecodebook in accordance with the received codebook subset constraintparameters; and determining active precoding matrices in the codebook inaccordance with the available matrices in each matrix set.

In a possible embodiment of the present disclosure, the step ofdetermining the active precoding matrices in the codebook in accordancewith the available matrices in each matrix set includes: with respect toeach precoding matrix in the codebook, determining whether or not allmatrices for generating the precoding matrix are available, anddetermining the precoding matrix where all the matrices are available asthe active precoding matrix; or with respect to each precoding matrix inthe codebook, determining whether or not there is at least one availablematrix in the matrices for generating the precoding matrix, anddetermining the precoding matrix where there is at least one availablematrix as the active precoding matrix.

In a possible embodiment of the present disclosure, the method furtherincludes: determining an active codebook of the codebook in accordancewith the determined active precoding matrix, and receiving a bitmapcorresponding to the active codebook, each bit of the bitmapcorresponding to a precoding matrix of the active codebook and beingused to indicate whether or not the precoding matrix is available forcalculating and returning CSI; and determining the precoding matrix inthe active codebook that is available for calculating and returning theCSI in accordance with the bitmap.

In a possible embodiment of the present disclosure, the method furtherincludes reporting matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation is used to indicate one or more available matrices, one ormore unavailable matrices, or a matrix-available weight value of eachmatrix in parts of or all the matrix sets.

In a possible embodiment of the present disclosure, the method furtherincludes: determining the matrix-available information in accordancewith usage times within a predetermined time period.

In yet another aspect, the present disclosure provides in someembodiments a device for constraining a codebook subset, including: aconstraint parameter determination module configured to determinecodebook subset constraint parameters for all or parts of matrix setsfor constructing a codebook respectively, each codebook subsetconstraint parameter indicating an available matrix in a correspondingmatrix set; and a constraint parameter transmission module configured totransmit the determined codebook subset constraint parameters to a UE.

In a possible embodiment of the present disclosure, the constraintparameter determination module is further configured to: determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with aconfiguration of an antenna array; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with an applicationscenario; or determine the codebook subset constraint parameters for allor parts of the matrix sets for constructing the codebook respectivelyin accordance with the configuration of the antenna array and theapplication scenario; or determine the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook respectively in accordance with a measurement result of anuplink signal transmitted by the UE; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with informationreturned by the UE; or determine the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook respectively in accordance with matrix-available informationreported by the UE.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the measurement result of the uplink signal transmittedby the UE, the constraint parameter determination module is furtherconfigured to: measure the uplink signal transmitted by the UE so as toobtain the measurement result; determine whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith the measurement result; and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in the case ofmeasuring the uplink signal transmitted by the UE so as to obtain themeasurement result, the constraint parameter determination module isfurther configured to: measure the uplink signal transmitted by the UE,so as to obtain a horizontal azimuth angle or a vertical azimuth angleof the UE, and in the case of determining whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith the measurement result, the constraint parameter determinationmodule is further configured to calculate an array response vectorcorrelation coefficient between each matrix in each matrix subset forconstructing the codebook and the horizontal azimuth angle or thevertical azimuth angle, compare the array response vector correlationcoefficient with an array response vector correlation coefficientthreshold, and determine whether or not the matrix is available inaccordance with a comparison result.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information returned by the UE, the constraintparameter determination module is further configured to: rank precodingmatrices in a descending order of usage times, select a predeterminednumber of precoding matrices with the largest usage times in accordancewith the information returned by the UE within a predetermined timeperiod, and determine matrices corresponding to the selected precodingmatrices; calculate a correlation coefficient between each matrix ineach matrix set for constructing the codebook and each of the determinedmatrices corresponding to the selected precoding matrices, compare thecorrelation efficient with a matrix correlation coefficient threshold,and determine whether or not the matrix in each matrix subset isavailable in accordance with a comparison result; and determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information about the matrix-available informationreported by the UE, the constraint parameter determination module isconfigured to: determine whether or not each matrix in each matrix setfor constructing the codebook is available in accordance with anavailable matrix indicated in the matrix-available information reportedby the UE, and determine the codebook subset constraint parameters forall or parts of the matrix sets for constructing the codebook inaccordance with a determination result; or determine whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with an unavailable matrix indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result; ordetermine whether or not each matrix in each matrix set for constructingthe codebook in accordance with a matrix-available weight valueindicated in the matrix-available information reported by the UE, anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook in accordance with adetermination result.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter is a bitmap, and each bit in the bitmap correspondsto a matrix in the matrix set and is used to indicate whether or not thematrix is available; or each codebook subset constraint parameterincludes a set of index values, and each index value corresponds to anavailable matrix in the matrix set; or each codebook subset constraintparameter is a bitmap, and each bit in the bitmap corresponds to amatrix subset in the matrix set and is used to indicate whether or notthe matrix subset is available; or each codebook subset constraintparameter includes a set of index values, and each index valuecorresponds to an available matrix subset in the matrix set.

In a possible embodiment of the present disclosure, the device furtherincludes a secondary constraint module configured to: determine anactive codebook of the codebook; generate a bitmap corresponding to theactive codebook, each bit in the bitmap corresponding to a precodingmatrix in the active codebook and being used to indicate whether or notthe precoding matrix is available for calculating and returning CSI; andtransmit the bitmap corresponding to the active codebook to the UE.

In still yet another aspect, the present disclosure provides in someembodiments a base station, including a processor, a memory and atransceiver. The processor is configured to read programs stored in thememory, so as to: determine codebook subset constraint parameters forall or parts of matrix sets for constructing a codebook respectively,each codebook subset constraint parameter indicating an available matrixin a corresponding matrix set; and transmit through the transceiver thedetermined codebook subset constraint parameters to a UE.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively, theprocessor is further configured to read the program stored in thememory, so as to: determine the codebook subset constraint parametersfor all or parts of the matrix sets for constructing the codebookrespectively in accordance with a configuration of an antenna array; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith an application scenario; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with theconfiguration of the antenna array and the application scenario; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith a measurement result of an uplink signal transmitted by the UE; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith information returned by the UE; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance withmatrix-available information reported by the UE.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the measurement result of the uplink signal transmittedby the UE, the processor is further configured to read the programstored in the memory, so as to: measure the uplink signal transmitted bythe UE so as to obtain the measurement result; determine whether or noteach matrix in each matrix set for constructing the codebook isavailable in accordance with the measurement result; and determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in the case ofmeasuring the uplink signal transmitted by the UE so as to obtain themeasurement result, the processor is further configured to read theprogram stored in memory, so as to measure the uplink signal transmittedby the UE, so as to obtain a horizontal azimuth angle or a verticalazimuth angle of the UE. In the case of determining whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with the measurement result, the processor is furtherconfigured to read the program stored in the memory, so as to calculatean array response vector correlation coefficient between each matrix ineach matrix subset for constructing the codebook and the horizontalazimuth angle or the vertical azimuth angle, compare the array responsevector correlation coefficient with an array response vector correlationcoefficient threshold, and determine whether or not the matrix isavailable in accordance with a comparison result.

In a possible embodiment of the present disclosure, in case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information returned by the UE, the processor isfurther configured to read the program stored in the memory, so as to:rank precoding matrices in a descending order of usage times, select apredetermined number of precoding matrices with the largest usage timesin accordance with the information returned by the UE within apredetermined time period, and determine matrices corresponding to theselected precoding matrices; calculate a correlation coefficient betweeneach matrix in each matrix set for constructing the codebook and each ofthe determined matrices corresponding to the selected precodingmatrices, compare the correlation efficient with a matrix correlationcoefficient threshold, and determine whether or not the matrix in eachmatrix subset is available in accordance with a comparison result; anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith a determination result.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information about the matrix-available informationreported by the UE, the processor is further configured to read theprogram stored in the memory, so as to: determine whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with an available matrix indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result; ordetermine whether or not each matrix in each matrix set for constructingthe codebook is available in accordance with an unavailable matrixindicated in the matrix-available information reported by the UE, anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook in accordance with adetermination result; or determine whether or not each matrix in eachmatrix set for constructing the codebook in accordance with amatrix-available weight value indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter is a bitmap, and each bit in the bitmap correspondsto a matrix in the matrix set and is used to indicate whether or not thematrix is available; or each codebook subset constraint parameterincludes a set of index values, and each index value corresponds to anavailable matrix in the matrix set; or each codebook subset constraintparameter is a bitmap, and each bit in the bitmap corresponds to amatrix subset in the matrix set and is used to indicate whether or notthe matrix subset is available; or each codebook subset constraintparameter includes a set of index values, and each index valuecorresponds to an available matrix subset in the matrix set.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the program stored in the memory, so as to:determine an active codebook of the codebook; generate a bitmapcorresponding to the active codebook, each bit in the bitmapcorresponding to a precoding matrix in the active codebook and used toindicate whether or not the precoding matrix is available forcalculating and returning CSI; and transmit through the transceiver thebitmap corresponding to the active codebook to the UE.

In still yet another aspect, the present disclosure provides in someembodiments a device for constraining a codebook subset, including: aconstraint parameter reception module configured to receive codebooksubset constraint parameters corresponding to all or parts of matrixsets for constructing a codebook, each codebook subset constraintparameter indicating an available matrix in a corresponding matrix set;an available matrix determination module configured to determineavailable matrices in each matrix set for constructing the codebook inaccordance with the received codebook subset constraint parameters; andan active precoding matrix determination module configured to determineactive precoding matrices in the codebook in accordance with theavailable matrices in each matrix set.

In a possible embodiment of the present disclosure, the active precodingmatrix determination module is further configured to: with respect toeach precoding matrix in the codebook, determine whether or not allmatrices for generating the precoding matrix are available, anddetermine the precoding matrix where all the matrices are available asthe active precoding matrix; or with respect to each precoding matrix inthe codebook, determine whether or not there is at least one availablematrix in the matrices for generating the precoding matrix, anddetermine the precoding matrix where there is at least one availablematrix as the active precoding matrix.

In a possible embodiment of the present disclosure, the device furtherincludes a secondary constraint module configured to: determine anactive codebook of the codebook in accordance with the determined activeprecoding matrix, and receive a bitmap corresponding to the activecodebook, each bit of the bitmap corresponding to a precoding matrix ofthe active codebook and being used to indicate whether or not theprecoding matrix is available for calculating and returning CSI; anddetermine the precoding matrix in the active codebook that is availablefor calculating and returning the CSI in accordance with the bitmap.

In a possible embodiment of the present disclosure, the device furtherincludes a matrix-available information reporting module configured toreport matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation is used to indicate one or more available matrices, one ormore unavailable matrices, or a matrix-available weight value of eachmatrix in parts or all the matrix sets.

In a possible embodiment of the present disclosure, the matrix-availableinformation determination module is further configured to determine thematrix-available information in accordance with usage times within apredetermined time period.

In still yet another aspect, the present disclosure provides in someembodiments a UE, including a processor, a memory and a transceiver. Theprocessor is configured to read programs stored in the memory, so as to:receive through the transceiver codebook subset constraint parameterscorresponding to all or parts of matrix sets for constructing acodebook, each codebook subset constraint parameter indicating anavailable matrix in a corresponding matrix set; determine availablematrices in each matrix set for constructing the codebook in accordancewith the received codebook subset constraint parameters; and determineactive precoding matrices in the codebook in accordance with theavailable matrices in each matrix set.

In a possible embodiment of the present disclosure, in the case ofdetermining the active precoding matrices in the codebook, the processoris further configured to read the program stored in the memory, so asto: with respect to each precoding matrix in the codebook, determinewhether or not all matrices for generating the precoding matrix areavailable, and determine the precoding matrix where all the matrices areavailable as the active precoding matrix; or with respect to eachprecoding matrix in the codebook, determine whether or not there is atleast one available matrix in the matrices for generating the precodingmatrix, and determine the precoding matrix where there is at least oneavailable matrix as the active precoding matrix.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the program stored in the memory, so as to:determine an active codebook of the codebook in accordance with thedetermined active precoding matrix, and receive through the transceivera bitmap corresponding to the active codebook, each bit of the bitmapcorresponding to a precoding matrix of the active codebook and beingused to indicate whether or not the precoding matrix is available forcalculating and returning CSI; and determine the precoding matrix in theactive codebook that is available for calculating and returning the CSIin accordance with the bitmap.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the program stored in the memory, so as toreport through the transceiver matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation is used to indicate one or more available matrices, one ormore unavailable matrices, or a matrix-available weight value of eachmatrix in parts or all the matrix sets.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the programs stored in the memory, so as todetermine the matrix-available information in accordance with usagetimes within a predetermined time period.

According to the embodiments of the present disclosure, the codebooksubset constraint parameters may be determined for all or parts of thematrix sets for constructing the codebook and then issued to the UE, andeach codebook subset constraint parameter indicates an available matrixin the corresponding matrix set, such that the UE may determine theavailable matrices in the matrix sets for constructing the codebook inaccordance with the codebook subset constraint parameters. The precodingmatrix is generated on the basis of the matrices, such that in the casethat the available matrices in the matrix sets have been obtained, it isable to determine the active precoding matrix, thereby to constrain thecodebook subset. The number of the matrices contained in the matrix setsfor constructing the codebook is fall less than the number of theprecoding matrices in the codebook, so the number of system resourcesfor the transmission of the codebook subset constraint parameters isfall smaller than the number of system resources for a conventionalmethod for constraining the codebook subset. As a result, it is able toreduce the number of the occupied system resources, thereby to reducesignaling overhead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for constraining a codebook subsetaccording to one embodiment of the present disclosure;

FIG. 2 is a flow chart of another method for constraining a codebooksubset according to one embodiment of the present disclosure;

FIG. 3 is a schematic view showing a device for constraining a codebooksubset according to one embodiment of the present disclosure;

FIG. 4 is a schematic view showing a base station according to oneembodiment of the present disclosure;

FIG. 5 is another schematic view showing a device for constraining acodebook subset according to one embodiment of the present disclosure;and

FIG. 6 is a schematic view showing a UE according to one embodiment ofthe present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be described hereinafter in conjunction withthe drawings and embodiments.

The present disclosure provides in some embodiments a method forconstraining a codebook subset at a base station side which, as shown inFIG. 1, includes the following steps.

Step 100: determining codebook subset constraint parameters for all orparts of matrix sets for constructing a codebook respectively, eachcodebook subset constraint parameter indicating an available matrix in acorresponding matrix set.

In some embodiments of the present disclosure, in the case that thecodebook subset constraint is performed with respect to UE indicated byA and a codebook A′ is stored in the UE indicated by A in FIG. 1, thecodebook in Step 100 is just the same as codebook A′ at the base stationside.

In the case that the codebook A′ consists of K matrix sets, P codebooksubset constraint parameters may be determined in Step 100. Eachcodebook subset constraint parameter corresponds to one matrix set inthe K matrix sets, where P may be equal to or smaller than K.

Step 110: transmitting the determined codebook subset constraintparameters to a UE.

In some embodiments of the present disclosure, an implementation mode ofStep 110 will not be particularly defined. For example, the determinedcodebook subset constraint parameters may be transmitted to the UEthrough high-layer signaling, or through physical-layer signaling, or inany other ways.

According to the method in the embodiments of the present disclosure,the codebook subset constraint parameters may be determined for all orparts of the matrix sets for constructing the codebook and then issuedto the UE, and each codebook subset constraint parameter indicates anavailable matrix in the corresponding matrix set, such that the UE maydetermine the available matrices in the matrix sets for constructing thecodebook in accordance with the codebook subset constraint parameters.The precoding matrix is generated on the basis of the matrices, suchthat in the case that the available matrices in the matrix sets havebeen obtained, it is able to determine the active precoding matrix,thereby to constrain the codebook subset. The number of the matricescontained in the matrix sets for constructing the codebook is fall lessthan the number of the precoding matrices in the codebook, so the numberof system resources for the transmission of the codebook subsetconstraint parameters is fall smaller than the number of systemresources for a conventional method for constraining the codebooksubset. As a result, it is able to reduce the number of the occupiedsystem resources, thereby to reduce signaling overhead.

In some embodiments of the present disclosure, there may be variousimplementation modes for Step 100, and some of them will be describedhereinafter.

First Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with a configuration of an antenna array.

In some embodiments of the present disclosure, the configuration of theantenna array may include, but be not limited to, a pattern of theantenna array, spacing between antenna units, and a polarizationdirection. The pattern of the antenna array may include, but be notlimited to, at least one of the number of antennae in a horizontaldimension and the number of antennae in a vertical dimension.

In the case of determining the codebook subset constraint parameters inaccordance with the configuration of the antenna array, matrices (i.e.,available matrices) which belong to the matrix sets for constructing thecodebook and match the configuration of the antenna array may bedetermined, so as to obtain the codebook subset constraint parameters.

For example, one matrix set for constructing the codebook is a set ofN-point Discrete Fourier Transformation (DFT) vectors, i.e., each matrixin the matrix set is a DFT vector and the matrix set includes N vectors.An m^(th) vector may be represented as

${V_{m} = \begin{bmatrix}1 & {e^{{- j}\; 2\pi\frac{m}{N}}\mspace{14mu}\ldots\mspace{14mu} e^{{- j}\; 2\pi\frac{m{({L - 1})}}{N}}}\end{bmatrix}^{T}},$where L represents a length of each vector. In the case that the spacingis a half of the carrier wavelength (i.e., the spacing is 0.5 times thecarrier wavelength), the available matrices may be selected using allvectors. In the case that the spacing between the antenna units is equalto a carrier wavelength, the available matrices may be selected usingthe following equation: {V_(m)}_(m=2i,i=0,1, . . . └N/2┘). And in thecase that the spacing is four times the carrier wavelength, theavailable matrices may be selected using the following equation:{V_(m)}_(m=4i,i=0,1, . . . └N/4┘).Second Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with an application scenario.

The application scenario may include, but be not limited to, spacingbetween the base stations, a height of a base station antenna, UE heightdistribution, and UE spatial angle distribution.

In the case of determining the codebook subset constraint parameters inaccordance with the application scenario, the matrices (i.e., theavailable matrices) which belong to the matrix sets for constructing thecodebook and match the application scenario may be determined, so as toobtain the codebook subset constraint parameters.

For example, one matrix set for constructing the codebook is a set of NDiscrete Fourier Transformation (DFT) vectors, i.e., each matrix in thematrix set is a DFT vector and the matrix set includes N vectors. Anm^(th) vector may be represented as

${V_{m} = \begin{bmatrix}1 & {e^{{- j}\; 2\pi\frac{m}{N}}\mspace{14mu}\ldots\mspace{14mu} e^{{- j}\; 2\pi\frac{m{({L - 1})}}{N}}}\end{bmatrix}^{T}},$where L represents a length of each vector. Each DFT vector maycorrespond to one spatial angle. The DFT vectors that match a UE spatialangle may be selected as the available matrices in accordance with theUE spatial angle distribution.Third Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with the configuration of the antenna arrayand the application scenario.

In the case of determining the codebook subset constraint parameters forall or parts of the matrix sets for constructing the codebookrespectively in accordance with the configuration of the antenna arrayand the application scenario, the matrices (i.e., the availablematrices) which belong to the matrix sets for constructing the codebookand match the configuration of the antenna array and the applicationscenario may be determined, so as to obtain the codebook subsetconstraint parameter.

Fourth Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with a measurement result of an uplink signaltransmitted by the UE.

There may exist various ways for this implementation mode. For example,the uplink signal from the UE may be measured so as to obtain ameasurement result, then whether or not each matrix in each matrix setfor constructing the codebook may be determined in accordance with themeasurement result, and then the codebook subset constraint parametersmay be determined for parts of or all the matrix sets in accordance witha determination result.

In the case that all the matrices in a certain matrix set are available,the codebook subset constraint parameter may be determined, or may notbe determined, for the matrix set.

The measured uplink signal may include, but be not limited to, an uplinkSounding Reference Signal (SRS).

Further, the measurement result obtained by measuring the uplink signaltransmitted by the UE may include, but be not limited to, a horizontalazimuth angle or a vertical azimuth angle of the UE. Correspondingly,the step of determining whether or not each matrix in each matrix setfor constructing the codebook respectively in accordance with themeasurement result may include calculating an array response vectorcorrelation coefficient between each matrix in each matrix subset forconstructing the codebook and the horizontal azimuth angle or thevertical azimuth angle, comparing the array response vector correlationcoefficient with an array response vector correlation coefficientthreshold, and determining whether or not the matrix is available inaccordance with a comparison result. For example, in the case that anarray response vector correlation coefficient between a certain matrixand the horizontal azimuth angle or the vertical azimuth angle isgreater than the array response vector correlation coefficientthreshold, the matrix may be an available matrix, and otherwise, it maybe an unavailable matrix.

The array response vector correlation coefficient threshold may be setin accordance with the practical need, or determined through simulation.

Of course, the measurement result obtained after measuring the uplinksignal may also be a channel. Correspondingly, matrices may be selectedin accordance with a signal obtained through the measurement, and thenthe matrices may be counted in a reverse manner so as to determine thematrices with higher adoption possibility, thereby to determine whetheror not the matrix is available.

It should be appreciated that, based on the fourth implementation mode,it is able to further determine the codebook subset constraintparameters in conjunction with the configuration of the antenna arrayand/or the application scenario.

Fifth Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with information returned by the UE.

There may exist various ways for this implementation mode. For example,precoding matrices may be ranked in a descending order of usage times, apredetermined number of precoding matrices with the largest usage timesmay be selected in accordance with the information returned by the UEwithin a predetermined time period, and matrices corresponding to theselected precoding matrices may be determined. Next, a correlationcoefficient between each matrix in each matrix set for constructing thecodebook and each of the determined matrices corresponding to theselected precoding matrices may be calculated and then compared with amatrix correlation coefficient threshold, and whether or not the matrixin each matrix subset is available may be determined in accordance witha comparison result. Finally, the codebook subset constraint parametersfor all or parts of the matrix sets for constructing the codebook may bedetermined respectively in accordance with a determination result. Forexample, in the case that a correlation coefficient between a certainmatrix and each of the determined matrices is greater than the matrixcorrelation coefficient threshold, the matrix may be an availablematrix, and otherwise, it may be an unavailable matrix.

The matrix correlation coefficient threshold may be set in accordancewith the practical need, or determined through simulation. Theinformation returned by the UE may include, but be not limited to, aPMI.

It should be appreciated that, based on the fifth implementation mode,it is able to further determine the codebook subset constraintparameters in conjunction with the configuration of the antenna arrayand/or the application scenario.

Sixth Implementation Mode for Step 100

In this mode, the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook may be determinedrespectively in accordance with matrix-available information reported bythe UE.

The matrix-available information may be used to specifically indicatewhether or not the matrix is available (i.e., to enable the UE torecommend the available matrix to the base station), or indicate amatrix-available weight value (i.e., the UE's preference regarding thematrix).

To be specific, whether or not each matrix in each matrix set forconstructing the codebook is available may be determined in accordancewith the available matrix indicated in the matrix-available informationreported by the UE, and then the codebook subset constraint parametersmay be determined for all or parts of the matrix sets in accordance witha determination result. The matrix-available information may be a bitmapand each bit in the bitmap may indicate whether or not a matrix isavailable, or the matrix-available information may be a set of indexvalues and each index value corresponds to an available matrix.

To be specific, whether or not each matrix in each matrix set forconstructing the codebook is available may be determined in accordancewith the unavailable matrix indicated in the matrix-availableinformation reported by the UE, and then the codebook subset constraintparameters may be determined for all or parts of the matrix sets inaccordance with a determination result. The matrix-available informationmay be a bitmap and each bit in the bitmap may indicate whether or not amatrix is available, or the matrix-available information may be a set ofindex values and each index value corresponds to an unavailable matrix.

To be specific, whether or not each matrix in each matrix set forconstructing the codebook is available may be determined in accordancewith the matrix-available weight value indicated in the matrix-availableinformation reported by the UE, and then the codebook subset constraintparameters may be determined for all or parts of the matrix sets inaccordance with a determination result. A larger matrix-available weightvalue means a larger preference value of the UE for the correspondingmatrix, so the matrix having a matrix-available weight value greaterthan a predetermined weight threshold may be determined as the availablematrix.

It should be appreciated that, based on the sixth implementation mode,it is able to further determine the codebook subset constraintparameters in conjunction with the configuration of the antenna arrayand/or the application scenario.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter may be a bitmap, and each bit in the bitmap maycorrespond to one matrix in the matrix set and may be used to indicatewhether or not the matrix is available. For example, in the case that abit has a value of 1, it means that the corresponding matrix isavailable, and in the case that a bit has a value of 0, it means thatthe corresponding matrix is unavailable. In another possible embodimentof the present disclosure, each bit in the bitmap may correspond to onematrix subset in the matrix set and may be used to indicate whether ornot the matrix subset is available. For example, in the case that a bithas a value of 1, it means that the corresponding matrix subset isavailable, and in the case that a bit has a value of 0, it means thatthe corresponding matrix subset is unavailable.

Each codebook subset constraint parameter may also include a set ofindex values, and each index value may correspond to one availablematrix in the matrix set or one available matrix subset in the matrixset.

In the case that one bit in the bitmap corresponds to one matrix subsetor one index value corresponds to one matrix subset, each matrix set maybe divided into several matrix subsets. The available matrix subsetrefer to a matrix subset in which all or parts of the matrices areavailable, and it may be determined according to the practical need orthrough simulation.

The matrix set may be divided in various ways, e.g., the matrices withan identical number of columns may belong to a matrix subset.

In a possible embodiment of the present disclosure, the codebook subsetconstraint may be performed for the second time. For example, an activecodebook of the codebook may be determined and then a bitmapcorresponding to the active codebook may be generated. Each bit in thebitmap may correspond to a precoding matrix in the active codebook andmay be used to indicate whether or not the precoding matrix is availablefor calculating and returning CSI. Then, the bitmap corresponding to theactive codebook may be transmitted to the UE. For another example, anactive codebook of the codebook may be determined and then a set ofindex values corresponding to the active codebook may be generated. Eachindex value may correspond to a precoding matrix in the active codebookthat is available for calculating and returning CSI. Then, the set ofindex values corresponding to the active codebook may be transmitted tothe UE. In another possible embodiment of the present disclosure, thecodebook subset constraint may be performed with respect to the activecodebook for the second time.

In some embodiments of the present disclosure, the active codebookrefers to a codebook consisting of active precoding matrices.

In some embodiments of the present disclosure, each active precodingmatrix refers to a precoding matrix generated by available matrices ineach matrix set for constructing the codebook.

The present disclosure further provides in some embodiments a method forconstraining a codebook subset at a UE side which, as shown in FIG. 2,includes the following steps.

Step 200: receiving codebook subset constraint parameters correspondingto all or parts of matrix sets for constructing a codebook, eachcodebook subset constraint parameter indicating an available matrix in acorresponding matrix set. The codebook in Step 200 is same as a codebookstored at the UE side.

Step 210: determining available matrices in each matrix set forconstructing the codebook in accordance with the received codebooksubset constraint parameters. In the case that all the matrices in amatrix set are available, no codebook subset constraint parameter may bereceived. In the case that no codebook subset constraint parametercorresponding to a certain matrix set has been received at the UE side,it means that all the matrices in the matrix set are available.

Step 220: determining active precoding matrices in the codebook inaccordance with the available matrices in each matrix set.

It may be defined that a precoding matrix is active only in the casethat all the matrices for generating the precoding matrix are available,or the precoding matrix is an active one as long as one matrix forgenerating the precoding matrix is available. Of course, the activeprecoding matrix may be defined in any other ways, which will not beparticularly defined herein.

According to the method in the embodiments of the present disclosure,the UE may receive the codebook subset constraint parameters for all orparts of the matrix sets for constructing the codebook, and eachcodebook subset constraint parameter indicates an available matrix inthe corresponding matrix set, such that the UE may determine theavailable matrices in the matrix sets for constructing the codebook inaccordance with the codebook subset constraint parameters. The precodingmatrix is generated on the basis of the matrices, such that in the casethat the available matrices in the matrix sets have been obtained, it isable to determine the active precoding matrix, thereby to constrain thecodebook subset. The number of the matrices contained in the matrix setsfor constructing the codebook is fall less than the number of theprecoding matrices in the codebook, so the number of system resourcesfor the transmission of the codebook subset constraint parameters isfall smaller than the number of system resources for a conventionalmethod for constraining the codebook subset. As a result, it is able toreduce the number of the occupied system resources, thereby to reducesignaling overhead.

After the determination of the active precoding matrix, the UE maymeasure and return CSI in accordance with the active precoding matrix inthe codebook. The UE may select the matrices merely from the activeprecoding matrix. There may exist two possible ways for the UE to returnthe CSI.

In a first way, a PMI returned by the UE may be an index value of theselected precoding matrix in an original codebook. At this time, it isimpossible to reduce the feedback overhead.

In a second way, the PMI returned by the UE may be an index value of theselected precoding matrix in an active codebook. The active codebook isa codebook consisting of the active precoding matrices in the originalcodebook. At this time, it is able to reduce the feedback overhead andthe calculation complexity of the UE.

In a possible embodiment of the present disclosure, the codebook subsetconstraint may be performed for the second time. For example, the activecodebook of the codebook may be determined in accordance with thedetermined active precoding matrices, and then a bitmap corresponding tothe active codebook may be received. Each bit in the bitmap maycorrespond to one precoding matrix in the active codebook and may beused to indicate whether or not the precoding matrix is available forcalculating and returning the CSI. Then, the precoding matrix in thecodebook that is available for calculating and returning the CSI may bedetermined in accordance with the bitmap.

In a possible embodiment of the present disclosure, the method furtherincludes reporting matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation indicates available matrices in parts of or all the matrixsets, or unavailable matrices in parts of or all the matrix sets, or amatrix-available weight value of each matrix in parts of or all thematrix sets. For example, the matrix-available weight value may bedefined as an integer within the range of 0 to 15 inclusively. In thecase that a matrix has a larger matrix-available weight value, it meansthe UE is inclined to make the matrix available.

In a possible embodiment of the present disclosure, the matrix-availableinformation may be determined in accordance with a number of usage timeswithin a predetermined time period.

For example, the UE may report the matrix-available informationperiodically. To be specific, in the case that the UE determines,through measurement, that a precoding matrix generated by some matricesin a matrix set is of less possibility to be selected by the UE, the UEmay notify the base station to set these matrices as unavailable.

In a possible embodiment of the present disclosure, the UE may furthercalculate and return CSI in accordance with the determined activeprecoding matrix. Of course, in the case that the codebook subsetconstraint has been performed for the second time, the CSI may becalculated and returned in accordance with the determined precodingmatrix that is available for calculating and returning the CSI.

The method in the embodiments of the present disclosure will bedescribed hereinafter in more details in conjunction with the followingapplication scenarios.

In one application scenario, the codebook A′ stored in UE1 consists oftwo matrix sets, and each precoding matrix in the codebook is generatedafter the calculation on matrices in the two matrix sets.

One of the matrix sets is marked as S1, and each matrix in the matrixset includes one column, i.e., a column vector. There are M1 vectors,i.e., V₁, V₂, . . . , and V_(M1).

The other matrix set is marked as S2, and each matrix in the matrix setincludes one column, i.e., a column vector. There are M2 vectors, i.e.,W₁, W₂, . . . , and W_(M2).

For example, each vector in the matrix set S1 is a DFT vector. In apossible embodiment of the present disclosure, the vectors are Q-pointDFT vectors, and Q=16, 32 and 64. In another possible embodiment of thepresent disclosure, M1=Q, so

${V_{m_{1}} = \begin{bmatrix}1 & {e^{{- j}\; 2\pi\frac{m_{1}}{Q}}\mspace{14mu}\ldots\mspace{14mu} e^{{- j}\; 2\pi\frac{m_{1}{({G - 1})}}{Q}}}\end{bmatrix}^{T}},$where G represents a length of the DFT vector, and m₁=1, 2, . . . , andM1.

For example, each vector in the matrix set S2 is a DFT vector. In apossible embodiment of the present disclosure, the vectors are Q-pointDFT vectors, and Q=16, 32 and 64. In another possible embodiment of thepresent disclosure, M2=Q, so

${W_{m_{2}} = \begin{bmatrix}1 & {e^{{- j}\; 2\pi\frac{m_{2}}{Q}}\mspace{14mu}\ldots\mspace{14mu} e^{{- j}\; 2\pi\frac{m_{2}{({G - 1})}}{Q}}}\end{bmatrix}^{T}},$where G represents a length of the DFT vector, and m₂=1, 2, . . . , andM2.

Hence, the codebook A′ with a rank being 1 may include the followingprecoding matrix:

$\begin{matrix}{\{ {\begin{bmatrix}{V_{m_{1}} \otimes W_{m_{2}}} \\{V_{m_{1}} \otimes W_{m_{2}}}\end{bmatrix},\begin{bmatrix}{V_{m_{1}} \otimes W_{m_{2}}} \\{{- V_{m_{1}}} \otimes W_{m_{2}}}\end{bmatrix}} \}_{{m_{1} = 1},2,\;\ldots\;,{M_{1};\;{m_{2} = 1}},2,\;\ldots\mspace{11mu},M_{2}},{or}} & (1) \\{\{ {\begin{bmatrix}{W_{m_{2}} \otimes V_{m_{1}}} \\{W_{m_{2}} \otimes V_{m_{1}}}\end{bmatrix},\begin{bmatrix}{W_{m_{2}} \otimes V_{m_{1}}} \\{W_{m_{2}} \otimes \;{- V_{m_{1}}}}\end{bmatrix}} \}_{{m_{1} = 1},2,\;\ldots\;,{M_{1};\;{m_{2} = 1}},2,\;\ldots\mspace{11mu},M_{2}}.} & (2)\end{matrix}$

In order to perform the codebook subset constraint on UE1, the basestation may determine the codebook subset constraint parameters. To bespecific, the codebook subset constraint parameters may be determined inaccordance with at least one of the configuration of the antenna arrayof the base station, the application scenario, the measurement resultobtained by measuring the uplink signal from the UE, the informationreturned by the UE, and the matrix-available information reported by theUE. In addition, the codebook subset constraint parameters may bedetermined for each of S1 and S2.

In the embodiment of the present disclosure, the codebook subsetconstraint parameters corresponding to the matrix set S1 may be a bitmapB1 with a length of M1, and each bit in the bitmap may correspond to onevector in the matrix set S1. The codebook subset constraint parameterscorresponding to the matrix set S2 may be a bitmap B2 with a length ofM2, and each bit in the bitmap may correspond to one vector in thematrix set S2. Hence, the active precoding matrix in the codebook mayinclude

$\begin{matrix}{\{ {\begin{bmatrix}{V_{m_{1}} \otimes W_{m_{2}}} \\{V_{m_{1}} \otimes W_{m_{2}}}\end{bmatrix},\begin{bmatrix}{V_{m_{1}} \otimes W_{m_{2}}} \\{{- V_{m_{1}}} \otimes W_{m_{2}}}\end{bmatrix}} \}_{{{m_{1} = 1},2,\;\ldots\;,{M_{1};\;{m_{2} = 1}},2,\;\ldots\mspace{11mu},M_{2}}{{{B\; 1{(m_{1})}} = 1},{{B\; 2{(m_{2})}} = 1}}},} & (3)\end{matrix}$where Bi(mi) represents an (mi)^(th) bit in the bitmap Bi.

It should be appreciated that, the codebook subset constraint parametersmay also be represented in the form of index values.

The base station may transmit the determined codebook subset constraintparameters to UE1. UE1 may then determine the available matrices in thematrix set S1 and the matrix set S2 in accordance with the receivedcodebook subset constraint parameters, e.g., UE1 may determine thematrices corresponding to the bits having a value of 1 in the bitmap asthe available matrices. Then, UE1 may determine the active precodingmatrix in the codebook A′ in accordance with the available matrices inthe matrix set S1 and the matrix set S2, with reference to the aboveformula (3). After the determination of the active precoding matrix, UE1may measure and return the CSI in accordance with the active precodingmatrix.

In another application scenario, the codebook A′ stored in UE1 consistsof two matrix sets (S1 and S2), and one block of each precoding matrixin the codebook is generated after the calculation on matrices in thetwo matrix sets.

The precoding matrix in the codebook A′ may be calculated through thefollowing formula:

$\begin{matrix}{{W = {{W_{1}W_{2}} = {\begin{bmatrix}{Z \otimes X} & 0 \\0 & {Z \otimes X}\end{bmatrix}W_{2}}}},} & (4)\end{matrix}$where Z represents a D_(z)×M_(z) matrix and belongs to the matrix setS1, and X represents a D_(x)×M_(x) matrix and belongs to the matrix setS2. The number of the matrices in the matrix set S1 is N_(z), and thenumber of the matrices in the matrix set S2 is N_(x).

In order to perform the codebook subset constraint on UE1, the basestation may determine the codebook subset constraint parameters. To bespecific, the codebook subset constraint parameters may be determined inaccordance with at least one of the configuration of the antenna arrayof the base station, the application scenario, the measurement resultobtained by measuring the uplink signal from the UE, the informationreturned by the UE, and the matrix-available information reported by theUE. In addition, the codebook subset constraint parameters may bedetermined for each of S1 and S2.

In the embodiment of the present disclosure, the codebook subsetconstraint parameters corresponding to the matrix set S1 may be a bitmapB1 with a length of N_(z), and each bit in the bitmap may correspond toone matrix in the matrix set S1. The codebook subset constraintparameters corresponding to the matrix set S2 may be a bitmap B2 with alength of N_(x), and each bit in the bitmap may correspond to one matrixin the matrix set S2.

A set of the available matrices in the matrix set S1 determined inaccordance with the codebook subset constraint parameters may be {Z₁,Z₂, . . . , Z_(L) ₁ }, where L1 represents the number of the availablematrices in the matrix set S1. A set of the available matrices in thematrix set S2 determined in accordance with the codebook subsetconstraint parameters may be {X₁, X₂, . . . , X_(L) ₂ }, where L2represents the number of the available matrices in the matrix set S2.

The active codebook consisting of the active precoding matrices in thecodebook A′ may be

$\begin{matrix}{\{ {\begin{bmatrix}{Z_{k} \otimes X_{l}} & 0 \\0 & {Z_{k} \otimes X_{l}}\end{bmatrix}W_{2}} \}_{{k = 1},\;\ldots\mspace{11mu},{L_{1};\;{l = 1}},\;\ldots\mspace{11mu},L_{2}}.} & (5)\end{matrix}$

It should be appreciated that, the codebook subset constraint parametersmay also be represented in the form of index values.

The base station may transmit the determined codebook subset constraintparameters to UE1. UE1 may then determine the available matrices in thematrix set S1 and the matrix set S2 in accordance with the receivedcodebook subset constraint parameters, e.g., determine the matricescorresponding to the bits having a value of 1 in the bitmap as theavailable matrices. Then, UE1 may determine the active precoding matrixin the codebook A′ in accordance with the available matrices in thematrix set S1 and the matrix set S2, with reference to the above formula(5).

Based on an identical inventive concept, the present disclosure furtherprovides in some embodiments a device for constraining a codebook subsetwhich, as shown in FIG. 3, includes: a constraint parameterdetermination module 301 configured to determine codebook subsetconstraint parameters for all or parts of matrix sets for constructing acodebook respectively, each codebook subset constraint parameterindicating an available matrix in a corresponding matrix set; and aconstraint parameter transmission module 302 configured to transmit thedetermined codebook subset constraint parameters to a UE.

In a possible embodiment of the present disclosure, the constraintparameter determination module is further configured to: determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with aconfiguration of an antenna array; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with an applicationscenario; or determine the codebook subset constraint parameters for allor parts of the matrix sets for constructing the codebook respectivelyin accordance with the configuration of the antenna array and theapplication scenario; or determine the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook respectively in accordance with a measurement result of anuplink signal transmitted by the UE; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with informationreturned by the UE; or determine the codebook subset constraintparameters for all or parts of the matrix sets for constructing thecodebook respectively in accordance with matrix-available informationreported by the UE.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the measurement result of the uplink signal transmittedby the UE, the constraint parameter determination module is furtherconfigured to: measure the uplink signal transmitted by the UE so as toobtain the measurement result; determine whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith the measurement result; and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in the case ofmeasuring the uplink signal transmitted by the UE so as to obtain themeasurement result, the constraint parameter determination module isfurther configured to: measure the uplink signal transmitted by the UE,so as to obtain a horizontal azimuth angle or a vertical azimuth angleof the UE, and in the case of determining whether or not each matrix ineach matrix set for constructing the codebook is available in accordancewith the measurement result, the constraint parameter determinationmodule is further configured to calculate an array response vectorcorrelation coefficient between each matrix in each matrix subset forconstructing the codebook and the horizontal azimuth angle or thevertical azimuth angle, compare the array response vector correlationcoefficient with an array response vector correlation coefficientthreshold, and determine whether or not the matrix is available inaccordance with a comparison result.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information returned by the UE, the constraintparameter determination module is further configured to: rank precodingmatrices in a descending order of usage times, select a predeterminednumber of precoding matrices with the largest usage times in accordancewith the information returned by the UE within a predetermined timeperiod, and determine matrices corresponding to the selected precodingmatrices; calculate a correlation coefficient between each matrix ineach matrix set for constructing the codebook and each of the determinedmatrices corresponding to the selected precoding matrices, compare thecorrelation efficient with a matrix correlation coefficient threshold,and determine whether or not the matrix in each matrix subset isavailable in accordance with a comparison result; and determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information about the matrix-available informationreported by the UE, the constraint parameter determination module isconfigured to: determine whether or not each matrix in each matrix setfor constructing the codebook is available in accordance with anavailable matrix indicated in the matrix-available information reportedby the UE, and determine the codebook subset constraint parameters forall or parts of the matrix sets for constructing the codebook inaccordance with a determination result; or determine whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with an unavailable matrix indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result; ordetermine whether or not each matrix in each matrix set for constructingthe codebook in accordance with a matrix-available weight valueindicated in the matrix-available information reported by the UE, anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook in accordance with adetermination result.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter is a bitmap, and each bit in the bitmap correspondsto a matrix in the matrix set and is used to indicate whether or not thematrix is available; or each codebook subset constraint parameterincludes a set of index values, and each index value corresponds to anavailable matrix in the matrix set; or each codebook subset constraintparameter is a bitmap, and each bit in the bitmap corresponds to amatrix subset in the matrix set and is used to indicate whether or notthe matrix subset is available; or each codebook subset constraintparameter includes a set of index values, and each index valuecorresponds to an available matrix subset in the matrix set.

In a possible embodiment of the present disclosure, the device furtherincludes a secondary constraint module configured to: determine anactive codebook of the codebook; generate a bitmap corresponding to theactive codebook, each bit in the bitmap corresponding to a precodingmatrix in the active codebook and being used to indicate whether or notthe precoding matrix is available for calculating and returning CSI; andtransmit the bitmap corresponding to the active codebook to the UE.

Based on an identical inventive concept, the present disclosure furtherprovides in some embodiments a base station which, as shown in FIG. 4,includes a processor 400, a memory 420 and a transceiver 410. Theprocessor 400 is configured to read programs stored in the memory 420,so as to: determine codebook subset constraint parameters for all orparts of matrix sets for constructing a codebook respectively, eachcodebook subset constraint parameter indicating an available matrix in acorresponding matrix set; and transmit through the transceiver 410 thedetermined codebook subset constraint parameters to a UE.

In FIG. 4, bus architecture may include a number of buses and bridgesconnected to each other, so as to connect various circuits for one ormore processors 400 and one or more memories 420. In addition, as isknown in the art, the bus architecture may be used to connect any othercircuits, such as a circuit for a peripheral device, a circuit for avoltage stabilizer and a power management circuit. Bus interfaces areprovided, and the transceiver 410 may consist of a plurality ofelements, i.e., a transmitter and a receiver for communication with anyother devices over a transmission medium. The processor 400 may takecharge of managing the bus architecture as well as general processings.The memory 420 may store data desired for the operation of the processor400.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively, theprocessor is further configured to read the programs stored in thememory, so as to: determine the codebook subset constraint parametersfor all or parts of the matrix sets for constructing the codebookrespectively in accordance with a configuration of an antenna array; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith an application scenario; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance with theconfiguration of the antenna array and the application scenario; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith a measurement result of an uplink signal transmitted by the UE; ordetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith information returned by the UE; or determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook respectively in accordance withmatrix-available information reported by the UE.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the measurement result of the uplink signal transmittedby the UE, the processor is further configured to read the programsstored in the memory, so as to: measure the uplink signal transmitted bythe UE so as to obtain the measurement result; determine whether or noteach matrix in each matrix set for constructing the codebook isavailable in accordance with the measurement result; and determine thecodebook subset constraint parameters for all or parts of the matrixsets for constructing the codebook respectively in accordance with adetermination result.

In a possible embodiment of the present disclosure, in the case ofmeasuring the uplink signal transmitted by the UE so as to obtain themeasurement result, the processor is further configured to read theprograms stored in memory, so as to measure the uplink signaltransmitted by the UE, so as to obtain a horizontal azimuth angle or avertical azimuth angle of the UE. In the case of determining whether ornot each matrix in each matrix set for constructing the codebook isavailable in accordance with the measurement result, the processor isfurther configured to read the programs stored in the memory, so as tocalculate an array response vector correlation coefficient between eachmatrix in each matrix subset for constructing the codebook and thehorizontal azimuth angle or the vertical azimuth angle, compare thearray response vector correlation coefficient with an array responsevector correlation coefficient threshold, and determine whether or notthe matrix is available in accordance with a comparison result.

In a possible embodiment of the present disclosure, in case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information returned by the UE, the processor isfurther configured to read the programs stored in the memory, so as to:rank precoding matrices in a descending order of usage times, select apredetermined number of precoding matrices with the largest usage timesin accordance with the information returned by the UE within apredetermined time period, and determine matrices corresponding to theselected precoding matrices; calculate a correlation coefficient betweeneach matrix in each matrix set for constructing the codebook and each ofthe determined matrices corresponding to the selected precodingmatrices, compare the correlation efficient with a matrix correlationcoefficient threshold, and determine whether or not the matrix in eachmatrix subset is available in accordance with a comparison result; anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith a determination result.

In a possible embodiment of the present disclosure, in the case ofdetermining the codebook subset constraint parameters for all or partsof the matrix sets for constructing the codebook respectively inaccordance with the information about the matrix-available informationreported by the UE, the processor is further configured to read theprograms stored in the memory, so as to: determine whether or not eachmatrix in each matrix set for constructing the codebook is available inaccordance with an available matrix indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result; ordetermine whether or not each matrix in each matrix set for constructingthe codebook is available in accordance with an unavailable matrixindicated in the matrix-available information reported by the UE, anddetermine the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook in accordance with adetermination result; or determine whether or not each matrix in eachmatrix set for constructing the codebook in accordance with amatrix-available weight value indicated in the matrix-availableinformation reported by the UE, and determine the codebook subsetconstraint parameters for all or parts of the matrix sets forconstructing the codebook in accordance with a determination result.

In a possible embodiment of the present disclosure, each codebook subsetconstraint parameter is a bitmap, and each bit in the bitmap correspondsto a matrix in the matrix set and is used to indicate whether or not thematrix is available; or each codebook subset constraint parameterincludes a set of index values, and each index value corresponds to anavailable matrix in the matrix set; or each codebook subset constraintparameter is a bitmap, and each bit in the bitmap corresponds to amatrix subset in the matrix set and is used to indicate whether or notthe matrix subset is available; or each codebook subset constraintparameter includes a set of index values, and each index valuecorresponds to an available matrix subset in the matrix set.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the programs stored in the memory, so as to:determine an active codebook of the codebook; generate a bitmapcorresponding to the active codebook, each bit in the bitmapcorresponding to a precoding matrix in the active codebook and used toindicate whether or not the precoding matrix is available forcalculating and returning CSI; and transmit through the transceiver thebitmap corresponding to the active codebook to the UE.

Based on an identical inventive concept, the present disclosure furtherprovides in some embodiments a device for constraining a codebook subsetwhich, as shown in FIG. 5, includes: a constraint parameter receptionmodule 501 configured to receive codebook subset constraint parameterscorresponding to all or parts of matrix sets for constructing acodebook, each codebook subset constraint parameter indicating anavailable matrix in a corresponding matrix set; an available matrixdetermination module 502 configured to determine available matrices ineach matrix set for constructing the codebook in accordance with thereceived codebook subset constraint parameters; and an active precodingmatrix determination module 503 configured to determine active precodingmatrices in the codebook in accordance with the available matrices ineach matrix set.

In a possible embodiment of the present disclosure, the active precodingmatrix determination module is further configured to: with respect toeach precoding matrix in the codebook, determine whether or not allmatrices for generating the precoding matrix are available, anddetermine the precoding matrix in which all the matrices are availableas the active precoding matrix; or with respect to each precoding matrixin the codebook, determine whether or not there is at least oneavailable matrix in the matrices for generating the precoding matrix,and determine the precoding matrix where there is at least one availablematrix as the active precoding matrix.

In a possible embodiment of the present disclosure, the device furtherincludes a secondary constraint module configured to: determine anactive codebook of the codebook in accordance with the determined activeprecoding matrix, and receive a bitmap corresponding to the activecodebook, each bit of the bitmap corresponding to a precoding matrix ofthe active codebook and being used to indicate whether or not theprecoding matrix is available for calculating and returning CSI; anddetermine the precoding matrix in the active codebook that is availablefor calculating and returning the CSI in accordance with the bitmap.

In a possible embodiment of the present disclosure, the device furtherincludes a matrix-available information reporting module configured toreport matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation is used to indicate an available matrix, an unavailablematrix, or a matrix-available weight value of each matrix.

In a possible embodiment of the present disclosure, the matrix-availableinformation determination module is further configured to determine thematrix-available information in accordance with usage times within apredetermined time period.

Based on an identical inventive concept, the present disclosure furtherprovides in some embodiments a UE which, as shown in FIG. 6, includes aprocessor 600, a memory 620 and a transceiver 610. The processor 600 isconfigured to read programs stored in the memory 620, so as to: receivethrough the transceiver 610 codebook subset constraint parameterscorresponding to all or parts of matrix sets for constructing acodebook, each codebook subset constraint parameter indicating anavailable matrix in a corresponding matrix set; determine availablematrices in each matrix set for constructing the codebook in accordancewith the received codebook subset constraint parameters; and determineactive precoding matrices in the codebook in accordance with theavailable matrices in each matrix set.

In FIG. 6, bus architecture may include a number of buses and bridgesconnected to each other, so as to connect various circuits for one ormore processors 600 and one or more memories 620. In addition, as isknown in the art, the bus architecture may be used to connect any othercircuits, such as a circuit for a peripheral device, a circuit for avoltage stabilizer and a power management circuit. Bus interfaces areprovided, and the transceiver 610 may consist of a plurality ofelements, i.e., a transmitter and a receiver for communication with anyother devices over a transmission medium. With respect to different UEs,a user interface 630 may also be provided for devices which are to bearranged inside or outside the UE, and these devices may include but benot limited to a keypad, a display, a speaker, a microphone and ajoystick. The processor 600 may take charge of managing the busarchitecture as well as general processings. The memory 620 may storetherein data for the operation of the processor 600.

In a possible embodiment of the present disclosure, in the case ofdetermining the active precoding matrices in the codebook, the processoris further configured to read the programs stored in the memory, so asto: with respect to each precoding matrix in the codebook, determinewhether or not all matrices for generating the precoding matrix areavailable, and determine the precoding matrix where all the matrices areavailable as the active precoding matrix; or with respect to eachprecoding matrix in the codebook, determine whether or not there is atleast one available matrix in the matrices for generating the precodingmatrix, and determine the precoding matrix where there is at least oneavailable matrix as the active precoding matrix.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the programs stored in the memory, so as to:determine an active codebook of the codebook in accordance with thedetermined active precoding matrix, and receive through the transceivera bitmap corresponding to the active codebook, each bit of the bitmapcorresponding to a precoding matrix of the active codebook and beingused to indicate whether or not the precoding matrix is available forcalculating and returning CSI; and determine the precoding matrix in theactive codebook that is available for calculating and returning the CSIin accordance with the bitmap.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the programs stored in the memory, so as toreport through the transceiver matrix-available information.

In a possible embodiment of the present disclosure, the matrix-availableinformation is used to indicate an available matrix(matrice), anunavailable matrix(matrice), or a matrix-available weight value of eachmatrix.

In a possible embodiment of the present disclosure, the processor isfurther configured to read the programs stored in the memory, so as todetermine the matrix-available information in accordance with usagetimes within a predetermined time period.

It should be appreciated that, the present disclosure may be provided asa method, a system or a computer program product, so the presentdisclosure may be in the form of full hardware embodiments, fullsoftware embodiments, or combinations thereof. In addition, the presentdisclosure may be in the form of a computer program product implementedon one or more computer-readable storage mediums (including but notlimited to disk memory, Compact Disc-Read Only Memory (CD-ROM) andoptical memory) including computer-readable program codes.

The present disclosure has been described with reference to the flowcharts and/or block diagrams of the method, device (system) and computerprogram product according to the embodiments of the present disclosure.It should be understood that computer program instructions may be usedto implement each of the work flows and/or blocks in the flow chartsand/or the block diagrams, and the combination of the work flows and/orblocks in the flow charts and/or the block diagrams. These computerprogram instructions may be provided to a processor of a commoncomputer, a dedicate computer, an embedded processor or any otherprogrammable data processing devices to create a machine, so thatinstructions executable by the processor of the computer or the otherprogrammable data processing devices may create a device to achieve thefunctions assigned in one or more work flows in the flow chart and/orone or more blocks in the block diagram.

These computer program instructions may also be stored in a computerreadable storage that may guide the computer or the other programmabledata process devices to function in a certain way, so that theinstructions stored in the computer readable storage may create aproduct including an instruction unit which achieves the functionsassigned in one or more flows in the flow chart and/or one or moreblocks in the block diagram.

These computer program instructions may also be loaded in the computeror the other programmable data process devices, so that a series ofoperation steps are executed on the computer or the other programmabledevices to create processes achieved by the computer. Therefore, theinstructions executed in the computer or the other programmable devicesprovide the steps for achieving the function assigned in one or moreflows in the flow chart and/or one or more blocks in the block diagram.

Although the preferred embodiments are described above, a person skilledin the art may make modifications and alterations to these embodimentsin accordance with the basic concept of the present disclosure. So, theattached claims are intended to include the preferred embodiments andall of the modifications and alterations that fall within the scope ofthe present disclosure.

The above are merely the preferred embodiments of the presentdisclosure, but the present disclosure is not limited thereto.Obviously, a person skilled in the art may make further modificationsand improvements without departing from the spirit of the presentdisclosure, and these modifications and improvements shall also fallwithin the scope of the present disclosure.

What is claimed is:
 1. A method for constraining a codebook subset,comprising steps of: measuring, by a network side device, the uplinksignal transmitted by a User Equipment (UE), so as to obtain ahorizontal azimuth angle or a vertical azimuth angle of the UE;calculating, by the network side device, an array response vectorcorrelation coefficient between each matrix in each matrix subset forconstructing the codebook and the horizontal azimuth angle or thevertical azimuth angle, comparing the array response vector correlationcoefficient with an array response vector correlation coefficientthreshold, and determining whether or not the matrix is available inaccordance with the comparing result; determining, by the network sidedevice, the codebook subset constraint parameters for all or parts ofthe matrix sets for constructing the codebook respectively in accordancewith the determining result; each codebook subset constraint parameterindicating an available matrix in a corresponding matrix set; andtransmitting, by the network side device, the determined codebook subsetconstraint parameters to the UE, wherein the available matrix is amatrix used for generating active precoding matrices among the matrixsets for constructing the codebook, wherein the active precodingmatrices in the codebook are determined in accordance with the availablematrices in each matrix set by: with respect to each precoding matrix inthe codebook, determining whether or not all matrices for generating theprecoding matrix are available, and determining the precoding matrixwhere all the matrices are available as the active precoding matrix; orwith respect to each precoding matrix in the codebook, determiningwhether or not there is at least one available matrix in the matricesfor generating the precoding matrix, and determining the precodingmatrix where there is at least one available matrix as the activeprecoding matrix, wherein each precoding matrix in the codebook isgenerated after a computation operation on matrices in the matrix sets;or one block of each precoding matrix in the codebook is generated aftera computation operation on matrices in the matrix sets.
 2. The methodaccording to claim 1, wherein each codebook subset constraint parameteris a bitmap, and each bit in the bitmap corresponds to a matrix in thematrix set and is used to indicate whether or not the matrix isavailable; or each codebook subset constraint parameter comprises a setof index values, and each index value corresponds to an available matrixin the matrix set; or each codebook subset constraint parameter is abitmap, and each bit in the bitmap corresponds to a matrix subset in thematrix set and is used to indicate whether or not the matrix subset isavailable; or each codebook subset constraint parameter comprises a setof index values, and each index value corresponds to an available matrixsubset in the matrix set.
 3. The method according to claim 1, furthercomprising: determining an active codebook of the codebook; generating abitmap corresponding to the active codebook, each bit in the bitmapcorresponding to a precoding matrix in the active codebook and beingused to indicate whether or not the precoding matrix is available forcalculating and returning Channel State Information (CSI); andtransmitting the bitmap corresponding to the active codebook to the UE.4. A base station, comprising a processor, a transceiver and a memory,wherein the processor is configured to read programs stored in thememory, so as to: measure the uplink signal transmitted by a UserEquipment (UE), so as to obtain a horizontal azimuth angle or a verticalazimuth angle of the UE; calculate an array response vector correlationcoefficient between each matrix in each matrix subset for constructingthe codebook and the horizontal azimuth angle or the vertical azimuthangle, compare the array response vector correlation coefficient with anarray response vector correlation coefficient threshold, and determinewhether or not the matrix is available in accordance with the comparingresult; determine the codebook subset constraint parameters for all orparts of the matrix sets for constructing the codebook respectively inaccordance with the determining result each codebook subset constraintparameter indicating an available matrix in a corresponding matrix set;and transmit through the transceiver the determined codebook subsetconstraint parameters to the UE, wherein the available matrix is amatrix used for generating the active precoding matrices among thematrix sets for constructing the codebook, wherein the active precodingmatrices in the codebook are determined in accordance with the availablematrices in each matrix set by: with respect to each precoding matrix inthe codebook, the processor being further configured for determiningwhether or not all matrices for generating the precoding matrix areavailable, and determining the precoding matrix where all the matricesare available as the active precoding matrix; or with respect to eachprecoding matrix in the codebook, the processor being further configuredfor determining whether or not there is at least one available matrix inthe matrices for generating the precoding matrix, and determining theprecoding matrix where there is at least one available matrix as theactive precoding matrix, wherein each precoding matrix in the codebookis generated after a computation operation on matrices in the matrixsets; or one block of each precoding matrix in the codebook is generatedafter a computation operation on matrices in the matrix sets.